The EP Tender is a car engine on a trailer that allows EVs to take long trips.

Inventor Jean-Baptiste Segard’s plan is to rent them to electric car owners for the occasional long trip at a very low rate.

He's discussed the idea with Renault and plans on pitching it other EV car makers.

The idea isn't new, but his version solves some of the technical challenges.

He patented a method that makes backing up a cinch. And while EVs can't typically be charged while driving, Segard says his devices get around this issue by essentially operating in parallel to the battery. It can work with an EV.

Could This Odd-Looking French Invention Solve The Electric Car’s Biggest Problem?

Still suffering from range anxiety? Just hitch this extra rental engine to the back of an EV and it could go on long-distance trips with no worries about recharging.

Freedom. The open road. The ability to pick up and just drive. This is the promise of the automobile, and the problem with the electric version: Even when what we actually do behind the wheel is sit in traffic on our way to the office, the thought of running out of batteries kills the fantasy.

But Jean-Baptiste Segard believes he has a solution, which he has discussed with Renault and plans on pitching to BMW, Volkswagen, and Ford Europe. "I will drive from Paris to Munich," he says, "and I'll say: ‘If you want to see an electric vehicle costing 15,000 euro which can drive a thousand kilometers, here it is!’"

The vehicle in this case would be a Renault Zoe, but the invention that makes a trip from Paris to Munich—a distance of roughly 500 miles—possible in a car with a range of closer to 60 miles is called the EP Tender. It is, essentially, a car engine on a trailer,that provides extra electricity for long drives. Segard’s plan is to rent them to electric car owners for the occasional long trip at a very low rate.

"It’s not new," says John O’Dell, green car analyst at Edmunds.com. In fact, the first range-extending trailers for electric cars date back at least since the early 1990s. AC Propulsion’s tzero—a precursor to the General Motors EV1 whose rise and fall is documented in the film Who Killed The Electric Car?—was making cross-country trips with the assistance of a gas-powered trailer in the 1990s.

Like the electric car itself, these early efforts failed to take off, and today the fate of the EP Tender is clearly linked to that of the EV market as a whole. "You need more than 10 EVs in a community to make much of a business case for it," notes O’Dell. Segard himself is, if possible, less optimistic. "At the moment the market is zero," he says.

It’s another version of the chicken-and-egg problem that electric cars face in general with fueling: It doesn’t make sense to build a national infrastructure for recharging (or a national rental business for EP Tenders) until more people drive electric cars, but one thing that holds back the electric cars is a better infrastructure for fueling (or a convenient way to occasionally extend the range of your electric car).

"I'm hopeful that, at the end of the day, [the car companies] will say market research demonstrates we could sell more car if we allow these cars to use EP Tender," says Segard.

Segard claims his devices solve the most obvious technical problems. He patented a mechanical method that makes backing up a cinch (which you can watch him demonstrate). Electric vehicles can’t typically be charged while driving, but Segard says his devices get around this issue by essentially operating in parallel to the battery, connecting between the battery and the inverter in a way that he says is compatible with all the EVs on the market. "They would fit very nicely on a Tesla Model S or a Nissan Leaf," he says.

The more immediate issue is simply getting electric car owners to install a trailer hitch. "I need to put a Tender next to the dealer that sells the first EV with a hitch," says Segard.

If it works as described, O’Dell thinks it has promise. "On a rental basis, they make sense," he says.